Constrained geometry metal complexes and methods for their preparation are disclosed in U.S. application Ser. No. 545,403. filed Jul. 3, 1990 (EP-A-416,815); U.S. application Ser. No. 547,718, filed Jul. 3, 1990 (EP-A-468,651); U.S. application Ser. No. 702,475, filed May 20, 1991 (EP-A-514,828); U.S. application Ser. No. 876,268, filed May 1, 1992. (EP-A-520,732) and U.S. application Ser. No. 8,003, filed Jan. 21, 1993 (WO 93/19104), as well as U.S. Pat. Nos. 5,055,438, 5,057,475, 5,096,867, 5,064,802, 5,132,380, and WO 95/00526. The teachings of all of the foregoing patents or the corresponding U.S. patent applications are hereby incorporated by reference.
U.S. Pat. Nos. 5,350,817 and 5,304,614 disclose zirconium complexes with bridged-metallocene ligands, wherein two indenyl groups are covalently linked together by a bridge containing carbon or silicon, which are useful for the polymerization of propylene.
EP-A-577,581 discloses unsymmetrical bis-Cp metallocenes containing a fluorene ligand with heteroatom substituents.
E. Barsties, S. Schaible; M.-H. Prosenc; U. Rief; W. Roll; O. Weyland; B. Dorerer; H.-H. Brintzinger J. Organometallic Chem. 1996, 520, 63-68, and H. Plenio; D. Birth J. Organometallic Chem. 1996, 519, 269-272 disclose systems in which the cyclopentadienyl ring of the indenyl is substituted with a dimethylamino group in non-bridged and Si-bridged bis-indenyl useful for the formation of isotactic polypropylene and polyethylene.
R. Leino; H. J. K. Luttikhedde; P. Lehmus; C.-E. Wilen; R. Sjoholm; A. Lehtonen; J. Seppala; J. H. Nasman Macromolecules, 1997, 30, 3477-3488 disclose C.sub.2 -bridged bis-indenyl metallocenes with oxygen in the 2-position of the indenyl group, and I. M. Lee; W. J. Gauthier; J. M. Ball; B. Iyengar: S. Collins Organometallics, 1992, 11, 2115-2122 discloses C.sub.2 -bridged bis-indenyl metallocenes with oxygen in the 5,6-positions of the indenyl group, while N. Piccolravazzi; P. Pino; G. Consiglio; A. Sironi; M. Moret Organometallics, 1990, 9, 3098-3105 discloses non-bridged bis-indenyl metallocenes with oxygen in the 4 and 7 positions of the indenyl group.
It has been thought that heteroatom-substitution, as opposed to carbon or H-substitution, on any position of the indenyl system of a metallocene complex, when used in an olefin polymerization catalyst, renders the catalyst less active, that is, there is lower catalyst productivity for polymerizations with .alpha.-olefins, and the polymer produced has lower molecular weight with lower tacticity. It has been suggested that the diminished activity of this broad class of catalysts is due to interaction of the heteroatom lone pair electrons with the Lewis acid cocatalyst polymerization activator, resulting in a more electronically deactivated Cp ring which is also more sterically hindered. SEE P. Foster; M. D. Rausch; J. C. W. Chien. J. Organometallic Chem. 1996, 519, 269-272.
Disclosure of random heteroatom substitution in mono-Cp metallocenes is found in EP-A-416,815, WO 95107942, WO 96/13529. U.S. Patent Nos. 5,096,867 and 5,621,126 and related cases.
Up to now it has been thought that heteroatom substitution in metallocene complexes for use as olefin polymerization catalysts would have disadvantages due to unwanted interactions of the lone pair electrons of the heteroatom either with the transition metal atom of the same or a different metallocene molecule, or with other components of the catalyst system.
Numerous improvements in various metallocene complexes used as olefin polymerization catalysts have been made. However, problems still remain with catalyst efficiency and deactivation of the catalyst under high temperature polymerization conditions. It would be advantageous to be able to produce polyolefins with higher molecular weights. It would also be advantageous to be able to improve other physical characteristics of the polymers produced by altering the substitution around the cyclopentadienyl group of the metallocene complexes used in olefin polymerization catalyst systems.